Project Summary: The long range objective of my research is to understand how the retina conveys visual information to the brain in the ensemble activity of many retinal ganglion cells, and how this signaling influences visual perception and behavior, in health and in disease. A major unsolved problem is how the patterns of activity in many cells communicate information not contained in the activity of individual cells. An important instance of this is synchronized firing, cases in which two or more cells fire spikes much more frequently than would be expected by chance. Substantial synchronized firing has been observed in retinas of several species. However, because synchronized firing cannot be measured with conventional single-unit recordings, nothing is known about synchronized firing in the primate retina, very little is known about synchrony in large groups of cells, and the impact of synchrony for vision is controversial. We will use unique large-scale recording techniques, applied to the primate retina, to (1) Test whether synchronized firing is present in primate retinal ganglion cells, and characterize its fundamental properties and mechanisms, (2) Test whether synchronized activity in many neurons is explained by pairwise synchronization or implicates more complex circuitry, and (3) Determine the effect of synchrony on visual signals transmitted from retina to brain. The rationale behind our approach is that techniques we have developed, including large scale recording from identified cell types in primate retina and analytical methods for measuring effects on visual signals, will qualitatively advance our understanding of the structure, origin, and function of synchronized firing. Relevance: Most aspects of vision involve the collective activity of many retinal neurons, so the proposed research will elucidate a fundamental function of the healthy visual system. Because the monkey visual system, and retina in particular, are very similar to their human counterparts, this work has the greatest possible potential for understanding disruption of retinal activity in disease, as well as designing prosthetic devices to replace the function of retinas damaged by photoreceptor disease.